Vanadium removal and recovery from aqueous solution with repeated use of a <scp>KOH</scp>‐modified seaweed biochar adsorbent: characterisation and removal mechanisms

Abstract BACKGROUND Vanadium (V) is a critical raw material which is extensively used in metallurgical, aerospace and chemical industries. However, V‐enriched wastewaters pose risks to human and environmental health due to their tendency to persist and bioaccumulate. Active V treatment processes generate significant quantities of byproducts with associated high operating costs and there is a need therefore to investigate novel passive technologies such as biosorption. This study investigates the capacity and reusability of KOH‐modified seaweed biochar (BC KOH ) to (re‐)adsorb, desorb and recover V, and evaluates the influences of initial V concentration, contact time, solution temperature and pH. RESULTS The maximum uptake of 48.8 mg V g −1 BC KOH occurred within 75 min and followed an exothermic adsorption process best described by the Langmuir isotherm model. The magnitude of enthalpy change suggested a physisorption binding interaction with optimum uptake in the range pH 3.5–4.5. Introduction of a saline content (100–400 mg Na + L −1 ) into the adsorption solution resulted in a modest reduction in the V adsorption level by BC KOH but further increases in saline concentration thereafter had only limited impact. Successive V(V) adsorption/desorption cycles indicated that V(V) binding to BC KOH displays effective reversibility with the adsorbent material demonstrating good regeneration characteristics. CONCLUSION BC KOH offers clear potential to be used as a cost‐effective passive and robust adsorbent of V within a range of acidic industrial waste streams. The capacity of the biochar to desorb and re‐adsorb demonstrates high V recovery potential and excellent biochar regeneration capability. © 2025 The Author(s). Journal of Chemical Technology and Biotechnology published by John Wiley &amp; Sons Ltd on behalf of Society of Chemical Industry (SCI).